This invention relates to an elevator control apparatus suitable for controlling several elevator functions.
In U.S. Pat. No. 2,674,348 to Santini et al., an automatic elevator system is disclosed in which inductor plates mounted along the elevator shaft are detected by sensors mounted on the elevator to give automatic slowdown and leveling control signals. A prime disadvantage of the Santini et al. system is that it requires a very close tolerance as to the position of the elevator within the shaft in order for the sensors to be properly oriented with respect to the fixed inductor plates. The problem of positioning the sensors adjacent the inductor plates makes the Santini et al. system very speed limited. Another disadvantage of that system is that for proper control, certain of the sensors must be switched off, depending on whether the elevator is moving upward or downward.
In U.S. Pat. No. 2,840,188 to Savage, an improvement to the Santini et al. system is described. In that system, the magnetic plates are mounted on a nonmagnetic ribbon which extends the length of the elevator shaft. Although the Savage system reduces the requirement for close tolerance as to the position of the elevator within the shaft, the system does require a guide system for the nonmagnetic ribbon; and the guide system, therefore, must nevertheless meet close tolerances. The magnetic sensors in the Savage system must be precisely positioned within a horizontal plane with respect to the tape in order that the sensor face will be parallel to the magnetic plates. As a result, the Savage system is also very speed limited in that wobbling of the tape can result in improper sensing of the magnetic plates or even cause the nonmagnetic ribbon to jump from its guides. Further, the Savage system is limited in the number of control functions available from a single tape.
In U.S. Pat. Nos. 3,674,113 and 3,765,510, the present inventor disclosed elevator control systems in which cams positioned along control wires activate mechanical switches on the elevator. Although those systems avoid the close tolerance requirements of the elevator position, they are speed limited due to the mechanical switching required. Further, although several functions can be controlled from a single wire, two wires are generally required where great flexibility in elevator control is required.
The above elevator control systems are adequate where an elevator does not travel at a speed more than about 200 feet per minute. However, with speeds greater than that, the close tolerance requirements or mechanical switching make those systems less useful. Further, in a building having a large number of floors, the cost and weight of the Savage ribbons and plates and the cost of multiple ribbon or wire systems can be prohibitive.
In light of the above prior art, it is an object of this invention to provide an elevator control system which is not so speed limited as past systems and which will be useful in a range of elevator speeds as high as 1800 feet per minute and more.
It is a further object of this invention to provide an elevator control system which avoids many of the requirements for close mechanical tolerances.
It is a further object of this invention to provide an elevator control system wherein the control elements are less weighty than prior art elements and wherein a single control element can control several elevator functions.